Wound dressings are used clinically to help manage the wound environment and to prevent wound breakdown. Wound management is defined as: the provision of the appropriate environment for healing by both direct and indirect methods together with the prevention of skin breakdown. Wound management practices today are based on wound bed preparation and the TIME concept, first introduced into practice in 2002 and then updated in 2012. The TIME acronym stands for:

• tissue;
• inflammation/infection;
• moisture; and
• edge.

The management of a wound involves consideration of all of these areas.¹ To be clear, managing a wound is not just taking a product off the shelf and applying it to a wound. The ideal wound dressing should: maintain a moist environment; absorb excess exudate; allow gaseous exchange; provide thermal insulation; provide a barrier to bacteria; be free from particulate/toxic components; be atraumatic on removal; be comfortable and conformable; protect the wound from further trauma; and be cost effective.^{2 3 4}

No one dressing will meet all the requirements of a wound, given that as the wound changes so the needs of the tissue change.^{5 6 7} Wound dressings are divided into two distinct groups – passive dressings and interactive dressings.^{5 7}

Passive wound dressings

For many years, the products used were of the ‘passive’ or ‘plug and conceal’ concept. Passive wound dressings include gauze, lint, nonstick dressings and tulle dressings; they have very few of the properties of an ideal dressing. Passive wound dressings have very limited (if any) use as primary dressing, but some are useful as secondary dressing.

Non-absorbent passive dressings are paraffin gauze (tulle) dressings, such as Jelonet™, these were among the earliest modern dressings. These products are known to adhere to the wound, causing trauma on removal, and require a secondary dressing. Their use is limited to simple clean superficial wounds and minor burns. They are also used as a primary dressing over skin grafts. There are modern alternative dressings, which are composed of synthetic fibres tightly meshed and impregnated with materials that allow moisture to pass through, minimising maceration, that will not allow tissue to pass through and thus not adhere to the wound surface, examples include: Adaptic™, Cuticerin™, Atrauman™.^{5 3 6 7 4}

Interactive wound dressings

These wound dressings help to control the microenvironment by combining with the exudate to form either a hydrophilic gel or by means of semipermeable membranes to control the flow of exudate from the wound into the dressing. They may also stimulate activity in the healing cascade and speed up the healing process. There are six classes of interactive dressings, classified according to their functionality.⁵

Film dressings

These dressings consist of a thin, polyurethane membrane coated with a layer of acrylic adhesive or an island version with a pad and are for wounds with no to low exudate. They are transparent, waterproof, gas/vapour permeable and flexible to protect from shear, friction, chemicals, microbes and spread tension forces. They are useful in superficial, clean wounds and in the prevention of breakdown and pre-ulcers in pressure wounds. They are also used as a postoperative dressing over sutures, to reduce sub-tissue tension and over closed wounds after the removal of the sutures or clips. If there is a small amount of exudate in the wound then an island film that includes a non-stick pad is best, for example, Opsite Post Op™ or Tegderm™ with pad. A new version, Opsite Post Op visible™, uses latticed foam as the pad to enable better absorption and allow the suture line to be observed. An acrylic padded version is also used on donor sites.^{5 3 6 7 4}

Hydrocolloid dressings

Hydrocolloids are a combination of polymers held in a fine suspension and often contain polysaccharides, proteins and adhesives; they are used on wounds with low exudate. When placed on a wound, the polymers combine with the exudate and form a soft, moist, gel-like mass. They also encourage autolysis to aid in the removal of slough from a wound.

These dressings are flexible, waterproof, provide physical barrier, gel with exudate, are debriding and require no secondary dressing, in other words, they are occlusive. Hydrocolloid products are used in low-exudating wounds, including ulcers, and granulating wounds. The thin form is used postoperatively over suture lines (such as Duoderm®, Comfeel™, Hydrocoll®). Please note that these dressing are contraindicated in diabetic wounds. ^{5 3 6 7 4}

Foam dressings

These products (for wounds with medium to high exudate) are soft, open-celled hydrophobic/ hydrophilic, non-adherent dressings that may be single or multiple layers and meet many of the properties of an ideal dressing. They absorb exudate; maintain a moist environment; and are thermally insulating, cushioning, nonadherent and non-residual.

Foams are used mainly in moderately to heavily exudating wounds, including ulcers, donor sites and minor burns, and they act as a secondary dressing – particularly as a covering with the use of amorphous hydrogels. In addition to standard and waterproof foams, T and shaped cavity devices may be inserted into cavity wounds or dehisced surgical wounds – examples include Lyofoam Max™and Allevyn™. There are specialised forms coated with a silicone adhesive that allows non-traumatic removal (such as Mepilex® and Allevyn Gentle®) these are very useful for older patients with fragile skin.^{5 3 6 7 4}

Alginate dressings

Alginates are the calcium or sodium/calcium salts of alginate acid, obtained from seaweed, for wounds with medium to high exudate. When applied to a wound, the sodium salts present in the wound exchange with the calcium in the alginate to form sodium alginate, a hydrophilic gel. This fibre has the ability to absorb exudate into itself while maintaining a moist environment. The dressings are highly absorbent, form gel with exudates, provide a moist interface, are easily removed and some are haemostatic. Alginates are used on donor sites, bleeding sites and exudating leg ulcers (Kaltostat®, Algisite M™, Sorbsan™ Comfeel Seasorb™).^{5 3 6 7 4}

Hydrofibre dressings

These dressings, for wounds with medium to high exudate, sharing some of the properties of alginates, are a fibre rope or dressing that forms a firm gel in contact with fluid. They are formed from a fibrous mat of carboxymethyl chitin (CMC) and are highly absorbent and have with no lateral wicking, which protects the peri-skin. Examples include Aquacel™.^{5 3 6 7}

Hydroactive dressings

These dressings are for wounds with medium to high exudate. Made of highly absorbent polymer, they are similar to foams; however, instead of holding exudate, the fluid is trapped within the polymer’s holes and the product swells. Hydroactive dressings are indicated for use in highly exudating surface and cavity wounds. Hydroactive dressings are not indicated for dry or lightly exudating wounds. Products in this category include Cutinova Hydro™, Biatane™ and Tielle™.^{5 3 6 7 4}

Hydrogels

Hydrogels are organic polymers with a high water content and are suitable for dry or sloughy wounds. They will rehydrate dry tissue and absorb certain amounts of fluid into themselves. They are provided as amorphous gels and are used to help re-hydrate sloughy and necrotic tissue to aid in the autolytic debridement of wounds (examples include, IntraSite gel™, Comfeel Purilon Gel™,Solosite™, DuoDERM Gel®, Solugel™). They are also used in the management of burns, including sunburn, scalds and other partial-thickness bums. Amorphous hydrogels have also been used in the management of chickenpox and shingles, applied to the eruptions three to four times a day. They provide a moist environment, relieve the discomfort of the lesion and also reduce the probability of scarring. Hydrogels are also available in sheet form, consisting of a cross-linked polymer and water held in a backing (Hydrosorb™, Nu-gel™). These products are particularly useful in the management of burns and also to aid the management of simple pressure wounds.^{5 3 6 7 4}

New hydrogels

Flaminal® hydrogels are based on gelled alginate and contain the enzymes glucose oxidase and lactoperoxidase to control the bioburden (by acting as an important natural antimicrobial). Flaminel has been shown to be bacteriostatic against Gram-positive organisms and exhibits pH-dependent bactericidal action against Gram-negative organisms in the presence of hydrogen peroxide and thiocyanate.^{8 9 10}

Miscellaneous wound dressings

There are a small number of specialised dressings for use in particular wound types. Cadexomer iodine dressings (Iodosorb/Iodoflex) feature a non-toxic iodophor, where the iodine is cross-linked into the structure of the polymer. When applied to the wound, the exudate combines with the polymer and iodine is released over 72 hours at 0.1 per cent (not cytotoxic). These wound dressings are used for sloughy/infected wounds, diabetic wounds and recalcitrant wounds and may stimulate healing.^{11 4 12}

Silver has been used for many years and it has proven broad-spectrum antimicrobial activity, with no documented cases of bacterial resistance reported. In particular, silver has been used in the treatment of burns as a silver sulphadiazine cream. Contemporary silver dressings allow for continuous release for up to seven days. The level of silver contained in the various dressings varies greatly. Their mode of action also varies – some release the silver into the wound; some partly release the silver, while still holding some in the dressing; and some keep the silver within the dressing. The choice of dressing will depend on the level of infection, the size and depth of the wound and the amount of exudate. Examples include, Acticoat®, Mepilex Ag®,Biatain Ag®, Aquacel Ag™ and Atrauman Ag™.

Devices used in wound management

Negative-pressure wound therapy (NPWT) is a therapeutic technique that uses a vacuum dressing to promote healing in acute or chronic wounds. It was first introduced in the late 1990s, and for some years there was little clinical evidence for its use; however, there is now significant published research reporting benefits. In particular, NPWT has a role in the management of major trauma, surgical incisional breakdown, large pressure wounds and late over skin grafts and some surgical wounds. In the area of obstetrics and gynaecology, there have been studies published on the role of NPWT in prevent wound complications following caesarean section in morbidly obese women, prophylactic use after caesarean delivery and use of NPWT over clean, closed surgical incisions.^{13 14 15 16 10}

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